A software-defined networking (SDN for short) network decouples control and data forwarding of a network device, network functions of a switch or a router are centralized in a controller, and a forwarding plane device performs only a data forwarding action.
During deployment of the SDN network in a large-scale distributed network, the network is usually divided into different segments. Each segment is referred to as an SDN domain, and multiple SDN domains are interconnected to form an entire SDN network. An SDN domain includes an SDN domain controller, a network controller, and a forwarding plane device. The SDN domain controller is a type of network controller. The forwarding plane device is mainly configured to perform data forwarding. The network controller performs configuration and management on the forwarding plane device by using a control channel. The SDN domain controller is configured to manage the network controller and the forwarding plane device in this domain. An application program in the network controller is used to modify a network behavior to adapt to different scenario requirements, for example, to provide a virtual network service, so that different logical functions can be implemented and mutually isolated in a same physical network.
In an SDN domain, by installing application programs on a network controller in a centralized manner, a network device in the SDN domain can implement complex network functions, such as routing control, tunnel encapsulation, firewall, secure access, and quality of service control. However, this manner brings extremely high running overheads to an SDN domain controller and the network controller, and causes a bottleneck in a control plane.